阶级 (jiē jí) refers specifically to social class in a political or economic sense, such as the working class or ruling class in Marxist theory. It is narrower than 阶层 (jiē céng), which can mean any social stratum or level, and more specific than 等级 (děng jí), which means grade or rank in any hierarchy (e.g., product grade, military rank). Use 阶级 for class struggle, class analysis, and class-based divisions in society.